Mysql anomoly

Hi, When I installed mysql server on my linode that all worked fine but I had a strange anomoly on my site (which doesn't actually use mysql). When I clicked through from a http page to a https page I got a 400 error (Request header field is missing ':' separator). This only happened in firefox. (I cleared cache etc. nothing worked).

Using Ubuntu 10.04 distro, Apache2, PHP5.

As soon as I removed mysql-server the site worked again!!

Any thoughts please? I would really appreciate to hear from anyone that might know what is going on. Thanks.